The present invention involves a knee protection device for a person sitting on a seat situated inside a motor vehicle. The device functions action in case of an accident-related deformation of the leg space of the interior space of the motor vehicle.
A knee protection device of this type is known for example from EP-A-0 684 164. It is proposed therein to provide, as a knee protection device, a rebound plate which comes into contact with the knee of the vehicle passenger during an accident-related deformation of the leg or knee space of the passenger compartment. On the backside, i.e. towards the dashboard, the rebound plate is connected to an airbag, which is filled instantaneously with gas from a gas generator upon a trigger signal. This solution makes it possible to design the leg and knee space of the motor vehicle as large as possible in the non-activated condition of the protection device, and nevertheless to instantaneously shift the rebound plate, as a passive restraint component, in the direction of the motor vehicle passenger during an impact of the motor vehicle.
The rebound plate prevents a high local introduction of force into the airbag by a knee contact and considerably increases the surface contributing to the energy absorption. Correspondingly, the required internal pressure in the airbag can turn out to be clearly reduced in comparison to a knee airbag without a rebound plate. This means that the airbag can be made of fabric conventional to the industry, and no expensive special material needs to be used, which would be expended for considerably higher internal pressures. Furthermore, one can get by with a considerably lower quantity of gas in comparison to systems without rebound plates. This can have a favorable effect on the reduction of the structural size of the generator so that sufficient space remains, for example, for storage areas in the dashboard of the motor vehicle.
It is found to be disadvantageous in the known knee protection device that the rebound plate, or also the load distribution plate, comes into a direct contact with the knees. According to such devices, the rigid mass of the plate hits on the knee directly.
From DE 296 11 869 U1 a knee restraint device is known for motor vehicles, in which an airbag is provided on the motor vehicle and in front of which a base plate is mounted, on which another so-called knee catch plate is placed towards the interior of the motor vehicle. This knee catch plate is made of foamed plastic and has within certain limits a damping effect during the initial contact with the knees of the vehicle passenger after an impact of the motor vehicle.
From DE 39 34 588 A1 a restraint system for the knee of a driver in a motor vehicle has become known, in which a first chamber facing towards the motor vehicle is a sheet metal hollow body, which connects to a wall which, with a covering, encloses a space housing a gas bag. The sheet metal hollow body should, in the activated condition, thereby form a deformation component which should be able to convert the impact energy of the knee over a relatively long distance. This system, on account of the sheet metal hollow body, is a relatively rigid system having a construction-based weight which is not insignificant, and thus has a relatively high injury potential if the vehicle passenger sits, for example, with his knee relatively close to the dashboard. The durability of the system could also be problematic, and here specifically at the bends of the sheet metal hollow body. After a relatively long standing time problems could occur at the bends in case of activation.